The few devs that make AU only, very very few, have been approached about VST so many times and are just not interested. i really don’t think it’s a big deal, all the best stuff is in VST and most of it even in VST3 (fabfilter, izotope, etc).
I completely agree with you… AU in cubase won’t ever happen.
I am pretty sure there are a couple mac vst plugins that don’t make it in Au format either.
Oh and yes, AU is a mac plugin format only… created by apple specifically for Logic initially. It was fair enough back then too, as they were better than VST2 in that you only needed one component file for all different output versions of the plugin, as well as some other advantages. But VST3 is better again. I just wish Avid hadn’t been stubborn with AAX and apple with AU… i just wish all daws simply used VST3, then all the plugin devs would port their plugins, there’d be one good standard… this is the way it should be. VST3 should be the midi of the plugin world.